Uses of Dare

In modern English, dare is not very common verb. In an informal style, people generally use other expressions. "He's not afraid to say what he thinks."

Dare is used both as a principal verb and as an auxiliary verb.

1. Dare as as a principal verb

As a principal verb 'dare' is used in the sense of 'defy, challenge or face boldly. Note that the principal verb dare is followed by an infinitive with to. It also has forms like dares or dared.
For examples:
She 'dared to swim' across the river.
How 'does he dare to do' it?

2. Dare as an auxiliary verb

The auxiliary verb 'dare' is followed by an infinitive without to. The auxiliary dare is common in questions and negative sentences. It doesn’t have forms like dares or dared. Questions and negatives(daren't) are made without do.

Examples:

He dare not do so. (NOT He dares not do so.)
She dare not take such a risk. (NOT She dares not to take such a risk.)
Dare she say that to him?
How dare he do such a thing?
She 'doesn't dare (to) go' out at night.
The old lady 'didn't dare (to) open' the door.

A special form 'daren't' (+ infinitive without 'to') is common in British English.
I 'daren't look'.
The third person singular daren't without -s.
She daren't tell him what she thinks.

Notes: (special expressions)

a. The expression I dare say(sometimes written 'I daresay) is no longer used with its original force. It now merely means ‘perhaps’, 'I think probably', 'I suppose'.
Examples:
I dare say he will agree to our proposal. (=Perhaps, he will agree to our proposal.)
I dare say that she is correct. (=Perhaps she is correct.)
'I dare say' it'll rain soon.
'I daresay' you're ready for a drink.

b. 'Don't you dare!' is sometimes used to discourage people from doing unwanted things.
Example: Mummy, can I draw a picture on the wall? ~ 'Don't you dare!'

c. 'How dare you?' is sometimes used as an indignant exclamation.
Example: 'How dare you?' Take your hands off me at once!

d. Children use the expression 'I dare you + infinitive' to challenge each other to do frightening things.
Example: 'I dare you to run' across the road with your eyes shut.